The invention is an improvement to a chuck assembly of the type having a chuck hub with a longitudinally extending bore therein the longitudinally extending bore having a closed end, an open end, and a radially extending bit bore in communication with the longitudinally extending bore, and a bit ball movable in the ball bore between a first retracted position out of the longitudinally extending bore and a second engaged position partially in the longitudinally extending bore. The inventive improvement includes a shuttle slidably disposed in the longitudinally extending bore. The shuttle has a first longitudinally extending portion having a first lateral dimension and a second longitudinally extending portion having a second, smaller lateral dimension. The shuttle is movable longitudinally between a first release position and a second lock position. The inventive improvement also includes a compression spring urging the shuttle away from the closed end of the longitudinally extending bore, and a shuttle ball disposed in a radially extending shuttle ball bore in the chuck hub which is in communication with the longitudinally extending bore of the chuck hub. The shuttle ball is movable in the shuttle ball bore between a first retracted position where the shuttle ball contacts the first longitudinally extending portion of the shuttle and a second extended position where the shuttle ball contacts the second longitudinally extending portion of the shuttle.